Support HostApplicationBuildersSettings for framework application (#665)

src/Microsoft.AspNetCore.SystemWebAdapters.FrameworkServices/Hosting/ConfigurationManagerConfigExtensions.cs

@@ -3,8 +3,11 @@
 
 using System.Collections;
 using System.Configuration;
+using System.Diagnostics;
+using System.Web.Hosting;
 using Microsoft.Extensions.Configuration;
 using Microsoft.Extensions.Configuration.Memory;
+using Microsoft.Extensions.Hosting;
 
 namespace Microsoft.AspNetCore.SystemWebAdapters.Hosting;
 
@@ -39,6 +42,41 @@ public static IConfigurationBuilder AddConfigurationManager(this IConfigurationB
 
         return builder;
     }
-}
 
+    public static IConfigurationManager UseHostingEnvironmentFallback(this IConfigurationManager configuration)
+    {
+        List<KeyValuePair<string, string?>>? optionList = null;
+
+        if (configuration[HostDefaults.ApplicationKey] is null)
+        {
+            optionList = new();
+            optionList.Add(new KeyValuePair<string, string?>(HostDefaults.ApplicationKey, HostingEnvironment.SiteName));
+        }
+
+        if (configuration[HostDefaults.EnvironmentKey] is null && (HostingEnvironment.IsDevelopmentEnvironment || IsIISExpress()))
+        {
+            optionList ??= new();
+            optionList.Add(new KeyValuePair<string, string?>(HostDefaults.EnvironmentKey, Environments.Development));
+        }
+
+        if (configuration[HostDefaults.ContentRootKey] is null)
+        {
+            optionList ??= new();
+            optionList.Add(new KeyValuePair<string, string?>(HostDefaults.ContentRootKey, HostingEnvironment.ApplicationPhysicalPath));
+        }
+
+        if (optionList is not null)
+        {
+            configuration.AddInMemoryCollection(optionList);
+        }
+
+        static bool IsIISExpress()
+        {
+            using var currentProcess = Process.GetCurrentProcess();
+
+            return string.Equals(currentProcess.ProcessName, "iisexpress", StringComparison.Ordinal);
+        }
 
+        return configuration;
+    }
+}

src/Microsoft.AspNetCore.SystemWebAdapters.FrameworkServices/Hosting/HttpApplicationHost.cs

@@ -1,8 +1,6 @@
 // Licensed to the .NET Foundation under one or more agreements.
 // The .NET Foundation licenses this file to you under the MIT license.
 
-using System.Diagnostics;
-using System.Web.Hosting;
 using Microsoft.Extensions.Configuration;
 using Microsoft.Extensions.DependencyInjection;
 using Microsoft.Extensions.Hosting;
@@ -28,31 +26,25 @@ internal HttpApplicationHost(IHost host)
         _current = this;
     }
 
-    public static HttpApplicationHostBuilder CreateBuilder()
+    public static HttpApplicationHostBuilder CreateBuilder() => CreateBuilder(new HostApplicationBuilderSettings());
+
+    internal static HttpApplicationHostBuilder CreateBuilder(HostApplicationBuilderSettings settings)
     {
-        var config = new ConfigurationManager();
+        if (settings is null)
+        {
+            throw new ArgumentNullException(nameof(settings));
+        }
 
-        config.AddConfigurationManager();
+        settings.Configuration ??= new ConfigurationManager();
+        settings.Configuration.AddConfigurationManager();
+        settings.Configuration.UseHostingEnvironmentFallback();
 
-        var builder = new HostApplicationBuilder(new HostApplicationBuilderSettings()
-        {
-            Configuration = config,
-            ApplicationName = HostingEnvironment.SiteName,
-            ContentRootPath = HostingEnvironment.ApplicationPhysicalPath,
-            EnvironmentName = HostingEnvironment.IsDevelopmentEnvironment || IsIISExpress() ? Environments.Development : Environments.Production
-        });
+        var builder = new HostApplicationBuilder(settings);
 
         builder.Services.AddSingleton<IHostLifetime, HttpApplicationLifetime>();
         builder.Services.AddConfigurationAccessor();
 
         return new(builder);
-
-        static bool IsIISExpress()
-        {
-            using var currentProcess = Process.GetCurrentProcess();
-
-            return string.Equals(currentProcess.ProcessName, "iisexpress", StringComparison.Ordinal);
-        }
     }
 
     public static void RegisterHost(Action<HttpApplicationHostBuilder> configure)